The present disclosure generally relates to three-dimensional road maps, and more specifically to determining features of a three-dimensional surface of a road (such as a pitch, grade, and bank of road surface). The three-dimensional maps can be provided to a navigation device for displaying road views.
A device featuring global positioning system (GPS) navigation typically receives GPS signals to determine the current location of the device. A GPS navigation system may display the location of the device relative to a road depicted in a map image to aid in navigation. For example, a navigation system may show an icon representing a vehicle in which the device is located relative to an image of a road within a map. As the device travels along a road toward an intersection (an example of a junction), the navigation system may show the icon gradually advancing toward an intersection shown in the map image. In some cases, a road of an intersection may pass over another road of the intersection. Because the navigation application displays a two-dimensional image of the intersection, it may not be possible for the driver to determine from the displayed image that a road passes over another road. And, even if the navigation device did know an ordering of the height of the roads, the image may be disorienting (e.g., the image might just show one road disappearing) since no height information leading up to an overpass (another example of a junction) is available.
Additionally, since such devices only receive two-dimensional information, the user has no visual cues about the terrain he/she will travel on or is currently traveling on, at least not from the navigation device. Given the flat two-dimensional views, providing directions and guidance via such navigational devices can be confusing. However, determining three-dimensional models of a road map is not easy unless one measures road heights at many locations, which would be very expensive.
Therefore, it is desirable to provide plausible three-dimensional (3D) road maps using existing two-dimensional (2D) road map information, e.g., just using simple ordering (stacking) information at junctions.